This invention relates to new and improved methods and apparatus for reconstituting the internal diameters of plastic sewer, water or drain pipes after the pipe is placed in and permanently located in situ in an earth bed or other underground earth base or covered location by vibration compacting or relocation of the bedding materials; and which, in addition, enhances the prevention of subsequent normally caused deformations in the diameter of such plastic pipes.
Heretofore, difficulties have been encountered in the use of plastic pipes subject to such diameter deflection or deformation in sewer, water and drain lines primarily because, when the earth covering backfill is applied to such pipes, the weight of the earth causes a deformation in the internal diameter of the plastic pipes, i.e., from circular to an ellipse or egg-shaped. Such egg-shaped deformations, of course, tended to result in leakage between the connected ends of the plastic pipe sections at the juncture of the connected ends of the plastic pipe sections at the juncture of the connections therebetween resulting in water waste, sewage leakage contamination and similar ecological problems.
Aside from the leakage of the sewage contamination of the soil when a high water table is encountered, we have a problem of infiltration or of ground water leaking into the pipe. In practically all sewage systems because of the grade required to flow raw sewage, it becomes necessary to install lift stations or lift pumps which are operated with electricity. When the infiltration occurs, this overloads the sewer and many times causes flooding of basements, etc. Also, with the excessive flow, the cost of electricity is increased. For these reasons, it is important to have a leak proof seal as now required by the Environmental Protection Agency.
The amount of flexible pipe deflection is very dependent on the type of soil, the density of the soil, the placement of the pipe and soil, and the moisture content of the soil. The plastic pipe will receive a certain amount of pressure from the backfill water, active and passive pressure superimposed loads and live loads.
As a consequence, government regulations have been promulgated which, not only define the earth covering requirements for such pipes in ditches, trenches, excavations and the like, but also, in the maximum allowable deformation of the internal diameter of the plastic pipes. At present, such government regulations permit such diameter deformation only to less than 5 percent of the internal diameter of the plastic pipe prior to its being buried in the earth and/or other bed materials.
To assure that this diameter deformation limitation is met by contractors installing such plastic pipes, these government regulations also set forth certain testing techniques, one of which is the commonly known ball technique. In this technique, a metal ball having a diameter which is comparable to 95 percent of the inside diameter of the plastic pipe is pulled through the pipe when in situ, generally from convenient locations, such as from manhole to adjacent manhole. In the event that the ball sticks in the pipe anywhere between the manhole inlet and the adjacent manhole outlet, the engineer requires the contractor to dig up the entire section of plastic pipe between the manholes and recompact the bedding material along the sides of pipe and under the haunches of the pipe and backfill the entire depth of the trench and allow the backfill to settle for at least 30 days and then retest that portion for deflection, resulting in a considerable unexpected financial and time loss to the contractor.